Circular polarization plate for organic EL display device and organic EL display device

ABSTRACT

There is provided a circularly polarizing plate for an organic EL display apparatus, which has an excellent antireflection function and has an excellent organic EL panel-protecting function. A circularly polarizing plate according to the present invention is used in an organic EL display apparatus. The circularly polarizing plate includes in this order: a polarizer; a retardation layer functioning as a λ/4 plate; a barrier layer; and a pressure-sensitive adhesive layer having a barrier function. An angle formed between an absorption axis of the polarizer and a slow axis of the retardation layer is from 35° to 55°.

TECHNICAL FIELD

The present invention relates to a circularly polarizing plate for anorganic EL display apparatus and an organic EL display apparatus.

BACKGROUND ART

In recent years, a display mounted with an organic EL panel (an organicEL display apparatus) has been proposed in association with widespreaduse of a thin display. The organic EL panel is liable to cause problems,such as ambient light reflection and background reflection, because thepanel includes a metal layer having high reflectivity. In view of theforegoing, it has been known that those problems are prevented byarranging a circularly polarizing plate on a viewer side (e.g., PatentLiteratures 1 to 3). The organic EL panel is extremely weak againstmoisture and oxygen in the air, and hence a barrier layer (barrier film)is typically arranged on the surface of the organic EL panel. However,there has been a growing demand for the impartment of a barrier functionto the circularly polarizing plate. Meanwhile, further thinning of thecircularly polarizing plate has also been continuously demanded.

CITATION LIST Patent Literature

[PTL 1] JP 2003-311239 A

[PTL 2] JP 2002-372622 A

[PTL 3] JP 3325560 B2

SUMMARY OF INVENTION Technical Problem

The present invention has been made to solve the conventional problems,and a primary object of the present invention is to provide a circularlypolarizing plate for an organic EL display apparatus, which has anexcellent antireflection function and has an excellent organic ELpanel-protecting function.

Solution to Problem

According to one aspect of the present invention, a circularlypolarizing plate for an organic EL display apparatus is provided. Thecircularly polarizing plate includes in this order: a polarizer; aretardation layer functioning as a λ/4 plate; a barrier layer; and apressure-sensitive adhesive layer having a barrier function, wherein anangle formed between an absorption axis of the polarizer and a slow axisof the retardation layer is from 35° to 55°.

In one embodiment of the invention, the circularly polarizing platefurther includes another retardation layer functioning as a λ/2 platebetween the polarizer and the retardation layer, wherein the angleformed between the absorption axis of the polarizer and the slow axis ofthe retardation layer is from 65° to 85°, and an angle formed betweenthe absorption axis of the polarizer and a slow axis of the anotherretardation layer is from 10° to 20°.

In one embodiment of the invention, the circularly polarizing platefurther includes a protective film between the polarizer and theretardation layer.

In one embodiment of the invention, the circularly polarizing platefurther includes a protective film between the polarizer and the anotherretardation layer.

In one embodiment of the invention, the circularly polarizing platefurther includes a protective film on a side of the polarizer oppositeto the retardation layer.

In one embodiment of the invention, the polarizer is elongated and hasthe absorption axis in a longitudinal direction thereof; and theretardation layer is elongated and has the slow axis in a direction atfrom 35° to 55° relative to a longitudinal direction thereof.

In one embodiment of the invention, the polarizer is elongated and hasthe absorption axis in a longitudinal direction thereof; and theretardation layer and the another retardation layer are elongated, andthe retardation layer has the slow axis in a direction at from 65° to85° relative to a longitudinal direction thereof, and the anotherretardation layer has the slow axis in a direction at from 10° to 20°relative to a longitudinal direction thereof.

In one embodiment of the invention, a ratio K/I of a potassium content(wt %) to an iodine content (wt %) in the polarizer is from 0.180 to0.235.

According to another aspect of the present invention, there is providedan organic EL display apparatus. The organic EL display apparatusincludes the circularly polarizing plate.

Advantageous Effects of Invention

According to the present invention, an organic EL panel-protectingfunction can be imparted by forming the barrier layer on the surface ofthe retardation layer in the circularly polarizing plate for an organicEL display apparatus. Further, according to the present invention, thebarrier layer can be formed while the optical characteristics andmechanical characteristics of the retardation film (retardation layer)are maintained within desired ranges. Accordingly, a circularlypolarizing plate that achieves both an excellent antireflection functionand an excellent organic EL panel-protecting function can be obtained.In addition, according to one embodiment of the present invention, onlyone λ/4 plate is used as the retardation layer and the λ/4 plate alsofunctions as the inner protective film of the polarizer, and hencesignificant thinning of the circularly polarizing plate can be achieved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view of a circularly polarizing plateaccording to one embodiment of the present invention.

FIG. 2 is a schematic sectional view of a circularly polarizing plateaccording to another embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Now, preferred embodiments of the present invention are described.However, the present invention is not limited to these embodiments.

Definitions of Terms and Symbols

The definitions of terms and symbols used herein are as follows.

(1) Refractive Indices (nx, ny, and nz)

A symbol “nx” represents a refractive index in a direction in which anin-plane refractive index is maximum (that is, slow axis direction),“ny” represents a refractive index in a direction perpendicular to theslow axis in the plane (that is, fast axis direction), and “nz”represents a refractive index in a thickness direction.

(2) In-Plane Retardation (Re)

The term “Re(λ)” refers to the in-plane retardation of a film measuredat 23° C. with light having a wavelength of λ nm. For example, the term“Re(550)” refers to the in-plane retardation of the film measured at 23°C. with light having a wavelength of 550 nm. The Re(λ) is determinedfrom the equation “Re=(nx−ny)×d” when the thickness of the film isrepresented by d (nm).

(3) Thickness Direction Retardation (Rth)

The term “Rth(λ)” refers to the thickness direction retardation of thefilm measured at 23° C. with light having a wavelength of λ nm. Forexample, the term “Rth(550)” refers to the thickness directionretardation of the film measured at 23° C. with light having awavelength of 550 nm. The Rth(λ) is determined from the equation“Rth=(nx−nz)×d” when the thickness of the film is represented by d (nm).

(4) Nz Coefficient

An Nz coefficient is determined from the equation “Nz=Rth/Re”.

A. Circularly Polarizing Plate

A-1. Entire Construction of Circularly Polarizing Plate

A circularly polarizing plate according to an embodiment of the presentinvention is used in an organic EL display apparatus. A circularlypolarizing plate according to one embodiment of the present inventionincludes, in this order, a polarizer, a retardation layer functioning asa λ/4 plate, a barrier layer, and a pressure-sensitive adhesive layerhaving a barrier function. A circularly polarizing plate according toanother embodiment of the present invention further includes anotherretardation layer functioning as a λ/2 plate between the polarizer andthe retardation layer. The entire construction of the circularlypolarizing plate is hereinafter specifically described for each of thosetypical embodiments, and then the respective layers and optical filmsconstituting the circularly polarizing plate are described in detail.

FIG. 1 is a schematic sectional view of the circularly polarizing plateaccording to one embodiment of the present invention. A circularlypolarizing plate 100 of this embodiment includes, a polarizer 10, aretardation layer 20, a barrier layer 30, and a pressure-sensitiveadhesive layer 40 in the stated order. As described above, theretardation layer 20 functions as a λ/4 plate and the pressure-sensitiveadhesive layer 40 has a barrier function. The circularly polarizingplate 100 of the illustrated example includes a protective film 50 onthe side of the polarizer opposite to the retardation layer 20. Inaddition, the circularly polarizing plate may include another protectivefilm (also referred to as “inner protective film”: not shown) betweenthe polarizer and the retardation layer. In the illustrated example, theinner protective film is omitted. In this case, the retardation layer 20can also function as the inner protective film. Such construction canachieve further thinning of the circularly polarizing plate.

In this embodiment, an angle formed between the absorption axis of thepolarizer 10 and the slow axis of the retardation layer 20 is from 35°to 55°, preferably from 38° to 52°, more preferably from 40° to 50°,still more preferably from 42° to 48°, particularly preferably from 44°to 46°. When the angle falls within such range, a desired circularpolarization function can be achieved. When reference is made to anangle in this description, the angle includes angles in both clockwiseand counterclockwise directions unless otherwise stated.

FIG. 2 is a schematic sectional view of the circularly polarizing plateaccording to another embodiment of the present invention. A circularlypolarizing plate 101 of this embodiment further includes anotherretardation layer 60 between the polarizer 10 and the retardation layer20. The another retardation layer 60 functions as a λ/2 plate. In thisembodiment, for convenience, the retardation layer 20 is referred to as“first retardation layer” and the another retardation layer 60 isreferred to as “second retardation layer” in some cases. The circularlypolarizing plate 101 of the illustrated example includes the protectivefilm 50 on the side of the polarizer opposite to the second retardationlayer. In addition, the circularly polarizing plate may include anotherprotective film (also referred to as “inner protective film”: not shown)between the polarizer and the second retardation layer. In theillustrated example, the inner protective film is omitted. In this case,the second retardation layer 60 can also function as the innerprotective film.

In this embodiment, the angle formed between the absorption axis of thepolarizer 10 and the slow axis of the first retardation layer 20 ispreferably from 65° to 85°, more preferably from 72° to 78°, still morepreferably about 75°. Further, an angle formed between the absorptionaxis of the polarizer 10 and the slow axis of the second retardationlayer 60 is preferably from 10° to 20°, more preferably from 13° to 17°,still more preferably about 15°. When the two retardation layers arearranged at such axial angles as described above, a circularlypolarizing plate having an extremely excellent circular polarizationcharacteristic (as a result, an extremely excellent antireflectioncharacteristic) in a wide wavelength range can be obtained.

A-2. Polarizer

Any appropriate polarizer may be adopted as the polarizer 10. Specificexamples thereof include: a product obtained by subjecting a hydrophilicpolymer film, such as a polyvinyl alcohol-based film, a partiallyformalized polyvinyl alcohol-based film, or an ethylene-vinyl acetatecopolymer-based partially saponified film, to dyeing treatment with adichromatic substance, such as iodine or a dichromatic dye, andstretching treatment; and a polyene-based alignment film, such as adehydration-treated product of polyvinyl alcohol or adehydrochlorination-treated product of polyvinyl chloride. Of those, apolarizer obtained by dyeing a polyvinyl alcohol-based film with iodineand uniaxially stretching the resultant is preferably used because ofits excellent optical characteristics.

The dyeing with iodine is performed by, for example, immersing thepolyvinyl alcohol-based film in an aqueous solution of iodine. Thestretching ratio of the uniaxial stretching is preferably from 3 timesto 7 times. The stretching may be performed after the dyeing treatmentor may be performed simultaneously with the dyeing. In addition, thestretching may be performed before the dyeing. The polyvinylalcohol-based film is subjected to, for example, swelling treatment,cross-linking treatment, washing treatment, or drying treatment asrequired. For example, when the polyvinyl alcohol-based film is washedwith water by being immersed in water before the dyeing, the soil orantiblocking agent on the surface of the polyvinyl alcohol-based filmcan be washed off. In addition, the polyvinyl alcohol-based film can beswollen to prevent dyeing unevenness or the like. The polyvinylalcohol-based film may be a single-layer film (film obtained by typicalfilm forming), or may be a polyvinyl alcohol-based resin layer formed ona resin substrate by application. A technology for the production of thepolarizer from the single-layer polyvinyl alcohol-based film is wellknown in the art. A technology for the production of the polarizer fromthe polyvinyl alcohol-based resin layer formed on the resin substrate byapplication is disclosed in, for example, JP 2009-098653 A.

The thickness of the polarizer is typically from about 1 μm to about 80μm.

In one embodiment, a ratio K/I of a potassium content (wt %) to aniodine content (wt %) in the polarizer is preferably from 0.180 to0.235, more preferably from 0.200 to 0.230. When the ratio K/I fallswithin such range, a polarizer having extremely excellent heatresistance can be obtained. As a result, a circularly polarizing platethat can achieve an organic EL display apparatus having extremelyexcellent durability can be obtained by a synergistic effect with thebarrier properties of the barrier layer and the pressure-sensitiveadhesive layer. In more detail, a circularly polarizing plate includinga polarizer having such ratio K/I typically shows a small change in huedue to heating. For example, a variation in a value (Hunter colorsystem) after the heating of the circularly polarizing plate at 95° C.for 500 hours is, for example, 7 or less, preferably 5 or less, morepreferably 3 or less.

The polarizer preferably contains a zinc component. Examples of the zinccomponent include zinc chloride and zinc sulfate. The incorporation ofthe zinc component can provide a polarizer having more excellentdurability.

A-3. Retardation Layer

As described above, the retardation layer 20 can function as a λ/4plate. The in-plane retardation Re(550) of such retardation layer isfrom 100 nm to 180 nm, preferably from 110 nm to 170 nm, more preferablyfrom 120 nm to 160 nm, particularly preferably from 135 nm to 155 nm.The retardation layer 20 typically has a refractive index ellipsoid ofnx>ny=nz or nx>ny>nz. In this description, for example, the expression“ny=nz” includes not only the case where the ny and the nz are strictlyequal to each other but also the case where the ny and the nz aresubstantially equal to each other. Therefore, the Nz coefficient of theretardation layer is, for example, from 0.9 to 2, preferably from 1 to1.5, more preferably from 1 to 1.3.

The thickness of the retardation layer may be set so that the layer mayfunction as a λ/4 plate most appropriately. In other words, thethickness may be set so that a desired in-plane retardation may beobtained. Specifically, the thickness is preferably from 10 μm to 80 μm,more preferably from 10 μm to 60 μm, most preferably from 30 μm to 50μm.

The retardation layer may show such a reverse wavelength dispersioncharacteristic that its retardation value increases in accordance withan increase in wavelength of measurement light, may show such a positivewavelength dispersion characteristic that the retardation value reducesin accordance with an increase in wavelength of the measurement light,or may show such a flat wavelength dispersion characteristic that theretardation value remains substantially unchanged even when thewavelength of the measurement light changes. The retardation layerpreferably shows a flat wavelength dispersion characteristic. Theadoption of a λ/4 plate (retardation layer) having a flat wavelengthdispersion characteristic can achieve an excellent antireflectioncharacteristic and an excellent reflection hue in an oblique direction.The retardation layer preferably has a ratio Re(450)/Re(550) of from0.99 to 1.03, and preferably has a ratio Re(650)/Re(550) of from 0.98 to1.02.

The retardation layer may include any appropriate resin film that cansatisfy such optical characteristics and mechanical characteristics asdescribed above. Typical examples of such resin include resins, forexample, transparent resins, such as a cellulose-based resin, apolyester-based resin, a polyvinyl alcohol-based resin, a polyvinylacetal-based resin, a polycarbonate-based resin, a polyamide-basedresin, a polyimide-based resin, a polyether sulfone-based resin, apolyether-based resin, a polysulfone-based resin, a polystyrene-basedresin, a cyclic olefin-based resin (a polynorbornene-based resin), apolyolefin-based resin, an acrylic resin, a urethane-based resin, anacrylic urethane-based resin, and an acetate-based resin. In anembodiment in which the retardation layer 20 is used alone, theretardation layer 20 may be preferably formed of a polycarbonate resin.The polycarbonate resin that may be used in this embodiment contains atleast a constituent unit derived from a dihydroxy compound having a bondstructure represented by the following structural formula (1), and isproduced by causing a dihydroxy compound including at least a dihydroxycompound having at least one bond structure —CH₂—O— in a moleculethereof and a carbonic acid diester to react with each other in thepresence of a polymerization catalyst.

CH₂—O

  (1)

A compound of any structure may be used as the dihydroxy compound havinga bond structure represented by the structural formula (1) as long asthe compound has two alcoholic hydroxy groups, contains a structurehaving a linking group —CH₂—O— in a molecule thereof, and can react withthe carbonic acid diester in the presence of the polymerization catalystto produce the polycarbonate resin. Two or more kinds of such compoundsmay be used in combination. In addition, a dihydroxy compound free ofany bond structure represented by the structural formula (1) may be usedas a dihydroxy compound to be used in the polycarbonate resin incombination with the above-mentioned dihydroxy compound. The dihydroxycompound having a bond structure represented by the structural formula(1) is hereinafter abbreviated as “dihydroxy compound (A)” and thedihydroxy compound free of any bond structure represented by thestructural formula (1) is abbreviated as “dihydroxy compound (B)” insome cases.

<Dihydroxy Compound (A)>

The “linking group —CH₂—O—” in the dihydroxy compound (A) means astructure that is bonded to an atom except a hydrogen atom to constitutea molecule. An atom to which at least an oxygen atom in the linkinggroup can be bonded, or each of atoms to which a carbon atom and theoxygen atom therein can be simultaneously bonded, is most preferably acarbon atom. The number of the “linking groups —CH₂—O—” in the dihydroxycompound (A) is 1 or more, preferably from 2 to 4.

More specific examples of the dihydroxy compound (A) include: compoundseach having an aromatic group in a side chain and an ether group bondedto an aromatic group in a main chain, such as9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, and9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene;bis(hydroxyalkoxyaryl)alkanes, such asbis[4-(2-hydroxyethoxy)phenyl]methane,bis[4-(2-hydroxyethoxy)phenyl]diphenylmethane,1,1-bis[4-(2-hydroxyethoxy)phenyl]ethane,1,1-bis[4-(2-hydroxyethoxy)phenyl]-1-phenylethane,2,2-bis[4-(2-hydroxyethoxy)phenyl]propane,2,2-bis[4-(2-hydroxyethoxy)-3-methylphenyl]propane,2,2-bis[3,5-dimethyl-4-(2-hydroxyethoxy)phenyl]propane,1,1-bis[4-(2-hydroxyethoxy)phenyl]-3,3,5-trimethylcyclohexane,1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane,1,4-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane,1,3-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane,2,2-bis[4-(2-hydroxyethoxy)-3-phenylphenyl]propane,2,2-bis[(2-hydroxyethoxy)-3-isopropylphenyl]propane,2,2-bis[3-tert-butyl-4-(2-hydroxyethoxy)phenyl]propane,2,2-bis[4-(2-hydroxyethoxy)phenyl]butane,2,2-bis[4-(2-hydroxyethoxy)phenyl]-4-methylpentane,2,2-bis[4-(2-hydroxyethoxy)phenyl]octane,1,1-bis[4-(2-hydroxyethoxy)phenyl]decane,2,2-bis[3-bromo-4-(2-hydroxyethoxy)phenyl]propane, and2,2-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]propane;bis(hydroxyalkoxyaryl)cycloalkanes, such as1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane,1,1-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]cyclohexane, and1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclopentane; dihydroxyalkoxydiarylethers, such as 4,4′-bis(2-hydroxyethoxy)diphenyl ether and4,4′-bis(2-hydroxyethoxy)-3,3′-dimethyl diphenyl ether;bishydroxyalkoxyaryl sulfides, such as 4,4′-bis(2-hydroxyethoxyphenyl)sulfide and 4,4′-bis[4-(2-dihydroxyethoxy)-3-methylphenyl] sulfide;bishydroxyalkoxyaryl sulfoxides, such as 4,4′-bis(2-hydroxyethoxyphenyl)sulfoxide and 4,4′-bis[4-(2-dihydroxyethoxy)-3-methylphenyl] sulfoxide;bishydroxyalkoxyaryl sulfones, such as4,4′-bis(2-hydroxyethoxyphenyl)sulfone and4,4′-bis[4-(2-dihydroxyethoxy)-3-methylphenyl]sulfone; and1,4-bishydroxyethoxybenzene, 1,3-bishydroxyethoxybenzene,1,2-bishydroxyethoxybenzene,1,3-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene,1,4-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene,4,4′-bis(2-hydroxyethoxy)biphenyl,1,3-bis[4-(2-hydroxyethoxy)phenyl]-5,7-dimethyladamantane, anhydroussugar alcohols typified by a dihydroxy compound represented by thefollowing formula (4), and compounds each having a cyclic etherstructure, such as a spiroglycol represented by the following generalformula (6). Those compounds may be used alone or in combinationthereof.

Those dihydroxy compounds (A) may be used alone or in combinationthereof. The dihydroxy compound represented by the formula (4) comes inisosorbide, isomannide, and isoidide that are in a stereoisomerrelationship. Those compounds may be used alone or in combinationthereof.

A usage ratio between the dihydroxy compound represented by the formula(4) and any other dihydroxy compound is as described later as a ratiobetween constituent units derived from the respective dihydroxycompounds constituting the polycarbonate resin. Of those dihydroxycompounds (A), isosorbide obtained by the dehydration condensation ofsorbitol produced from various starches that are abundant as resourcesand are hence easily available is most preferred in terms of the ease ofavailability and the ease of production, optical characteristics, andformability.

Isosorbide is liable to be gradually oxidized by oxygen. Accordingly, itis important that when the isosorbide is stored or handled at the timeof the production of the polycarbonate resin, a deoxidant be used or anitrogen atmosphere be established for preventing its decomposition dueto oxygen. In addition, it is necessary that moisture be prevented frombeing included in the isosorbide. The oxidation of the isosorbideproduces decomposition products typified by formic acid. For example,when the polycarbonate resin is produced by using isosorbide containingthose decomposition products, the decomposition products are responsiblefor the occurrence of the coloring of the polycarbonate resin to beobtained or for remarkable deterioration of its physical properties. Inaddition, the decomposition products affect a polymerization reactionand hence a polymer having a high molecular weight is not obtained insome cases.

Further, when a stabilizer that prevents the occurrence of formic acidis added to isosorbide, depending on the kind of the stabilizer, thecoloring of the polycarbonate resin to be obtained occurs or itsphysical properties are remarkably deteriorated in some cases. Areducing agent or an antacid is used as the stabilizer. Of those, thereducing agent is, for example, sodium borohydride or lithiumborohydride, and the antacid is, for example, sodium hydroxide. However,when such alkali metal salt is added, its alkali metal also serves as apolymerization catalyst. Accordingly, excessive addition of the salt maypreclude the control of the polymerization reaction.

In order to obtain isosorbide free of any oxidative decompositionproduct, isosorbide may be distilled as required. In addition, also inthe case where a stabilizer is compounded for preventing the oxidationor decomposition of the isosorbide, the isosorbide may be distilled asrequired in order that the stabilizer may be removed. In this case, thedistillation of the isosorbide may be simple distillation or may becontinuous distillation, and is not particularly limited. With regard tothe atmosphere under which the distillation is performed, after an inertgas atmosphere, such as argon or nitrogen, has been established, thedistillation is performed under reduced pressure.

For example, when isosorbide is subjected to such distillation, itspurity may be set to such a high value that its formic acid content isless than 20 ppm, preferably 10 ppm or less, more preferably 5 ppm orless, still more preferably 3 ppm or less, or the isosorbide isparticularly preferably completely free of formic acid. Simultaneously,the purity may be set to such a high value that the content of an alkalimetal compound and/or an alkaline earth metal compound with respect to 1mol of the isosorbide is 10 μmol or less, preferably 5 μmol or less,more preferably 3 μmol or less, still more preferably 1 μmol or less interms of a metal, or the isosorbide is particularly preferablycompletely free of any alkali metal compound and/or any alkaline earthmetal compound.

In the polycarbonate resin to be used in the present invention, thedihydroxy compound (A), such as a dihydroxy compound represented by thegeneral formula (1), having a formic acid content of less than 20 ppm ispreferably used. Further, the formic acid content is preferably 10 ppmor less, more preferably 5 ppm or less, still more preferably 3 ppm orless, or the dihydroxy compound (A) is particularly preferablycompletely free of formic acid produced by its decomposition or thelike. When the dihydroxy compound (A), such as the dihydroxy compoundrepresented by the formula (4), having such high purity is used as a rawmaterial, a problem in the polymerization reaction to be described lateris solved, and hence a high-quality polycarbonate resin furthersuppressed in coloring and the like can be stably and efficientlyproduced.

Although specific means for subjecting the dihydroxy compound (A), suchas the dihydroxy compound represented by the formula (4), having smallcontents of formic acid, and the alkali metal compound and/or thealkaline earth metal compound as described above to the reaction withthe carbonic acid diester is not particularly limited, for example, thefollowing method may be adopted.

The dihydroxy compound (A), such as the dihydroxy compound representedby the formula (4), having a high purity is preferably stored under anatmosphere where oxygen is absent, such as an inert gas atmosphere, or areduced-pressure or vacuum atmosphere, until a time point immediatelybefore the reaction with the carbonic acid diester. When the compound isstored under an environment at 40° C. and 80% RH after having beenremoved from the storage state, the compound is supplied to a reactionsystem with the carbonic acid diester typically within 2 weeks, morepreferably within 1 week. In the case of the storage under theenvironment at 40° C. and 80% RH, even when the dihydroxy compoundrepresented by the formula (4) is left to stand in air for typically 2weeks or less, preferably 1 week or less, the polymerization is notinhibited. When the temperature and the humidity are less than 40° C.and 80% RH, respectively, the storage period can be lengthened.

The term “under the inert gas atmosphere” as used herein means, forexample, that the compound is stored under an atmosphere containing oneor two or kinds of gases, such as nitrogen and argon, the atmospherehaving an oxygen content of 1,000 ppm or less, especially an atmospherecompletely free of oxygen, and the term “under the reduced-pressureatmosphere” means, for example, that the compound is stored under anatmosphere having a pressure of 13.3 kPa or less and an oxygen contentof 100 ppm or less. In the storage system, a deoxidant using iron powderas a main component, for example, a deoxidant, such as AGELESS(manufactured by Mitsubishi Gas Chemical Company, Inc.) or OXY-EATER(manufactured by Ueno Fine Chemicals Industry, Ltd.), or a drying agent,such as silica gel, a molecular sieve, or aluminum oxide, may be causedto coexist as required.

In addition, the oxidation of the dihydroxy compound (A), such asisosorbide, produces decomposition products typified by formic acid, andhence it is effective to store the compound at low temperature so thatthe decomposition products may not be produced.

As long as the storage temperature is 40° C. or less, when anenvironment having an oxygen concentration of 1,000 ppm or less ismaintained under an inert gas atmosphere by causing a deoxidant tocoexist, the compound can be subjected to the polymerization for atleast 1 month. The storage temperature is 40° C. or less, preferably 25°C. or less, more preferably 10° C. or less, particularly preferably 5°C. or less.

Although powdery or flaky isosorbide can be stored under a humidity ashigh as 80% RH, its mass may change owing to moisture absorption.Accordingly, the isosorbide is preferably hermetically stored in analuminum moisture barrier bag or the like, or stored under an inert gasatmosphere so as not to absorb moisture.

Further, those conditions may be appropriately used in combination.

When the dihydroxy compound (A), such as the dihydroxy compoundrepresented by the formula (4), is subjected to the reaction with thecarbonic acid diester to be described later, the form of the compound isnot particularly limited, and may be a powder form, may be a flake form,or may be a liquid form, such as a molten state or an aqueous solution.

<Dihydroxy Compound (B)>

In the polycarbonate resin, a dihydroxy compound (B), which is adihydroxy compound except the dihydroxy compound (A), may be used as thedihydroxy compound. As the dihydroxy compound (B), for example, analicyclic dihydroxy compound, an aliphatic dihydroxy compound, anoxyalkylene glycol, an aromatic dihydroxy compound, or a diol having acyclic ether structure may be used as the dihydroxy compound serving asa structural unit of polycarbonate, in combination with the dihydroxycompound (A), such as the dihydroxy compound represented by the formula(4).

Although the alicyclic dihydroxy compound that may be used in thepolycarbonate resin is not particularly limited, a compound typicallycontaining a five-membered ring structure or a six-membered ringstructure is preferably used. In addition, the six-membered ringstructure may be fixed in a chair shape or a boat shape by a covalentbond. When the alicyclic dihydroxy compound has the five-membered ringor six-membered ring structure, the heat resistance of the polycarbonateresin to be obtained can be improved. The number of carbon atoms in thealicyclic dihydroxy compound is typically 70 or less, preferably 50 orless, more preferably 30 or less. As the value increases, the heatresistance is improved. However, it becomes difficult to synthesize thecompound, it becomes difficult to purify the compound, or cost for thecompound increases. As the number of carbon atoms reduces, it becomeseasy to purify the compound and the compound becomes more easilyavailable.

Specific examples of the alicyclic dihydroxy compound containing afive-membered ring structure or a six-membered ring structure includealicyclic dihydroxy compounds each represented by the following generalformula (II) or (III):HOCH₂—R¹—CH₂OH  (II)HO—R²—OH  (III)in the formulae (II) and (III), R¹ and R² each represent a cycloalkylenegroup having 4 to 20 carbon atoms.

Cyclohexanedimethanol serving as the alicyclic dihydroxy compoundrepresented by the general formula (II) encompasses various isomers ineach of which R¹ in the general formula (II) is represented by thefollowing general formula (IIa), where R³ represents an alkyl grouphaving 1 to 12 carbon atoms or a hydrogen atom. Specific examplesthereof include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,and 1,4-cyclohexanedimethanol.

Tricyclodecanedimethanol or pentacyclopentadecanedimethanol serving asthe alicyclic dihydroxy compound represented by the general formula (II)encompasses various isomers in each of which R¹ in the general formula(II) is represented by the following general formula (IIb), where nrepresents 0 or 1.

Decalindimethanol or tricyclotetradecanedimethanol serving as thealicyclic dihydroxy compound represented by the general formula (II)encompasses various isomers in each of which R¹ in the general formula(II) is represented by the following general formula (IIc), where mrepresents 0 or 1. Specific examples thereof include2,6-decalindimethanol, 1,5-decalindimethanol, and 2,3-decalindimethanol.

In addition, norbornanedimethanol serving as the alicyclic dihydroxycompound represented by the general formula (II) encompasses variousisomers in each of which R¹ in the general formula (II) is representedby the following general formula (IId). Specific examples thereofinclude 2,3-norbornanedimethanol and 2,5-norbornanedimethanol.

Adamantanedimethanol serving as the alicyclic dihydroxy compoundrepresented by the general formula (II) encompasses various isomers ineach of which R¹ in the general formula (II) is represented by thefollowing general formula (IIe). A specific example thereof is1,3-adamantanedimethanol.

In addition, cyclohexanediol serving as the alicyclic dihydroxy compoundrepresented by the general formula (III) encompasses various isomers ineach of which R² in the general formula (III) is represented by thefollowing general formula (IIIa), where R³ represents an alkyl grouphaving 1 to 12 carbon atoms or a hydrogen atom. Specific examplesthereof include 1,2-cyclohexanediol, 1,3-cyclohexanediol,1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol.

Tricyclodecanediol or pentacyclopentadecanediol serving as the alicyclicdihydroxy compound represented by the general formula (III) encompassesvarious isomers in each of which R² in the general formula (III) isrepresented by the following general formula (IIIb), where n represents0 or 1.

Decalindiol or tricyclotetradecanediol serving as the alicyclicdihydroxy compound represented by the general formula (III) encompassesvarious isomers in each of which R² in the general formula (III) isrepresented by the following general formula (IIIc), where m represents0 or 1. As the decalindiol or the tricyclotetradecanediol, there may bespecifically used, for example, 2,6-decalindiol, 1,5-decalindiol, or2,3-decalindiol.

Norbornanediol serving as the alicyclic dihydroxy compound representedby the general formula (III) encompasses various isomers in each ofwhich R² in the general formula (III) is represented by the followinggeneral formula (IIId). As the norbornanediol, there may be specificallyused, for example, 2,3-norbornanediol or 2,5-norbornanediol.

Adamantanediol serving as the alicyclic dihydroxy compound representedby the general formula (III) encompasses various isomers in each ofwhich R² in the general formula (III) is represented by the followinggeneral formula (IIIe). As the adamantanediol, there may be specificallyused, for example, 1,3-adamantanediol.

Of the above-mentioned specific examples of the alicyclic dihydroxycompound, in particular, cyclohexanedimethanols,tricyclodecanedimethanols, adamantanediols, andpentacyclopentadecanedimethanols are preferred, and1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,1,2-cyclohexanedimethanol, and tricyclodecanedimethanol are preferredfrom the viewpoints of the ease of availability and the ease ofhandling.

Examples of the aliphatic dihydroxy compound that may be used includeethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol,1,3-butanediol, 1,2-butanediol, 1,5-heptanediol, and 1,6-hexanediol.

Examples of the oxyalkylene glycols that may be used include diethyleneglycol, triethylene glycol, tetraethylene glycol, and polyethyleneglycol.

Examples of the aromatic dihydroxy compound that may be used include2,2-bis(4-hydroxyphenyl)propane [=bisphenol A],2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane,2,2-bis(4-hydroxy-3,5-diethylphenyl)propane,2,2-bis(4-hydroxy-(3,5-diphenyl)phenyl)propane,2,2-bis(4-hydroxy-3,5-dibromophenyl)propane,2,2-bis(4-hydroxyphenyl)pentane, 2,4′-dihydroxy-diphenylmethane,bis(4-hydroxyphenyl)methane, bis(4-hydroxy-5-nitrophenyl)methane,1,1-bis(4-hydroxyphenyl)ethane, 3,3-bis(4-hydroxyphenyl)pentane,1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)sulfone,2,4′-dihydroxydiphenyl sulfone, bis(4-hydroxyphenyl) sulfide,4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxy-3,3′-dichlorodiphenylether, 4,4′-dihydroxy-2,5-diethoxydiphenyl ether,9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene,9,9-bis[4-(2-hydroxyethoxy-2-methyl)phenyl]fluorene,9,9-bis(4-hydroxyphenyl)fluorene, and9,9-bis(4-hydroxy-2-methylphenyl)fluorene.

Examples of the diol having a cyclic ether structure that may be usedinclude spiroglycols and dioxane glycols.

The exemplified compounds are examples of the alicyclic dihydroxycompound, the aliphatic dihydroxy compound, the oxyalkylene glycol, thearomatic dihydroxy compound, and the diol having a cyclic etherstructure that may be used in the present invention, and the dihydroxycompound (B) is by no means limited thereto. One or two or more kinds ofthose compounds may be used together with the dihydroxy compoundrepresented by the formula (4).

The use of any such dihydroxy compound (B) can provide effects, such asan improvement in flexibility, an improvement in heat resistance, and animprovement in formability, in accordance with applications. Althoughthe ratio of the dihydroxy compound (A), such as the dihydroxy compoundrepresented by the formula (4), to all the dihydroxy compoundsconstituting the polycarbonate resin is not particularly limited, theratio is preferably 10 mol % or more, more preferably 40 mol % or more,still more preferably 60 mol % or more, and is preferably 90 mol % orless, more preferably 80 mol % or less, still more preferably 70 mol %or less. When the content of a constituent unit derived from any otherdihydroxy compound is excessively large, the performance of the resin,such as optical characteristics, may be reduced.

When the alicyclic dihydroxy compound out of the other dihydroxycompounds is used, the ratio of the total of the dihydroxy compound (A),such as the dihydroxy compound represented by the formula (4), and thealicyclic dihydroxy compound to all the dihydroxy compounds constitutingthe polycarbonate resin is not particularly limited, but is preferably80 mol % or more, more preferably 90 mol % or more, particularlypreferably 95 mol % or more.

In addition, although a content ratio between a constituent unit derivedfrom the dihydroxy compound (A), such as the dihydroxy compoundrepresented by the formula (4), and a constituent unit derived from thealicyclic dihydroxy compound in the polycarbonate resin may be selectedfrom any appropriate ratios, a ratio “constituent unit derived from thedihydroxy compound represented by the formula (4):constituent unitderived from the alicyclic dihydroxy compound” is preferably from 1:99to 99:1 (mol %), and the ratio “constituent unit derived from thedihydroxy compound represented by the formula (4):constituent unitderived from the alicyclic dihydroxy compound” is particularlypreferably from 10:90 to 90:10 (mol %). When the content of theconstituent unit derived from the dihydroxy compound represented by theformula (4) exceeds the range and the content of the constituent unitderived from the alicyclic dihydroxy compound falls below the range, thecoloring of the resin is liable to occur. In contrast, when the contentof the constituent unit derived from the dihydroxy compound representedby the formula (4) falls below the range and the content of theconstituent unit derived from the alicyclic dihydroxy compound exceedsthe range, the following tendency is observed: the molecular weight ofthe resin hardly increases.

Further, when the aliphatic dihydroxy compound, the oxyalkylene glycol,the aromatic dihydroxy compound, and the diol having a cyclic etherstructure are used, the ratio of the total of the dihydroxy compound(A), such as the dihydroxy compound represented by the formula (4), andthe respective dihydroxy compounds to all the dihydroxy compoundsconstituting the polycarbonate resin is not particularly limited, andmay be selected from any appropriate ratios. In addition, a contentratio between the constituent unit derived from the dihydroxy compound(A), such as the dihydroxy compound represented by the formula (4), anda constituent unit derived from each of those dihydroxy compounds isalso not particularly limited, and may be selected from any appropriateratios.

Here, the polymerization degree of the polycarbonate resin having theconstituent units derived from the dihydroxy compounds (which ishereinafter sometimes referred to as “polycarbonate copolymer”) ispreferably 0.40 dl/g or more, more preferably 0.43 dl/g or more in termsof a reduced viscosity measured as follows: a solution is preciselyprepared by using a mixed solution containing phenol and1,1,2,2-tetrachloroethane at a mass ratio of 1:1 as a solvent so as tohave a polycarbonate concentration of 1.00 g/dl, and its reducedviscosity is measured at a temperature of 30.0° C.±0.1° C. (the reducedviscosity is hereinafter simply referred to as “reduced viscosity of thepolycarbonate”). In addition, the polymerization degree is typically2.00 dl/g or less, preferably 1.60 dl/g or less. When the reducedviscosity of the polycarbonate is excessively low, the mechanicalstrength of a molded article obtained by molding the polycarbonatecopolymer is weak in many cases. In addition, when the reduced viscosityof the polycarbonate increases, the following tendency is observed: theflowability of the polycarbonate copolymer at the time of the moldingreduces to reduce its cycle characteristic and to lengthen its moldingcycle, and the birefringence of the molded article to be obtained isliable to be large.

In addition, the Abbe number of the polycarbonate resin is preferably 20or more, more preferably 50 or more, particularly preferably 55 or more.As the value increases, the wavelength dispersion of a refractive indexof the resin reduces and hence a chromatic aberration reduces.Accordingly, the resin becomes suitable as an optical film. As the Abbenumber reduces, the wavelength dispersion of the refractive indexincreases and hence the chromatic aberration increases. Therefore, thevalue for the Abbe number is preferably as large as possible, and anupper limit therefor is not particularly limited.

In addition, the 5% thermal weight loss temperature of the polycarbonateresin is preferably 340° C. or more, more preferably 345° C. or more. Asthe 5% thermal weight loss temperature increases, the resin is improvedin thermal stability and hence can be used at higher temperatures. Inaddition, the temperature at which the resin is produced can beincreased and hence a temperature control width at the time of theproduction can be widened. Accordingly, the production is facilitated.As the 5% thermal weight loss temperature reduces, the thermal stabilityreduces and hence it becomes difficult to use the resin at hightemperatures. In addition, an allowable width for the control at thetime of the production narrows to make it difficult to produce theresin. Therefore, an upper limit for the 5% thermal weight losstemperature is not particularly limited, and the temperature isdesirably as high as possible. The decomposition temperature of thecopolymer serves as the upper limit.

In addition, the Izod impact strength of the polycarbonate resin ispreferably 30 J/m² or more. An upper limit for the Izod impact strengthis not particularly limited because as the Izod impact strengthincreases, a molded body obtained by molding the resin is increased instrength and hence becomes less likely to break.

In addition, in the polycarbonate resin, the amount of a produced gasexcept a phenol component at 110° C. per unit area (hereinaftersometimes simply referred to as “amount of a produced gas”) ispreferably 5 ng/cm² or less, and the amount of a produced gas derivedfrom a dihydroxy compound except the dihydroxy compound represented bythe formula (4) is more preferably 0.5 ng/cm² or less.

When the polycarbonate resin is subjected to differential scanningcalorimetry (DSC), the resin provides a single glass transitiontemperature. However, when the kinds of the dihydroxy compoundrepresented by the formula (4) and the alicyclic dihydroxy compound, anda compounding ratio therebetween are adjusted, the glass transitiontemperature can be adjusted, i.e., the resin can be obtained as apolymer having any appropriate glass transition temperature rangingfrom, for example, about 45° C. to about 155° C. in accordance withapplications.

In a film application, flexibility is typically required. Accordingly,the glass transition temperature of the polycarbonate resin ispreferably adjusted to 45° C. or more, for example, from 45° C. to 130°C.

The polycarbonate resin preferably has at least two of the physicalproperties at the same time, and more preferably further has any otherphysical property together therewith.

The polycarbonate resin may be produced by a melt polymerization methodinvolving causing the dihydroxy compounds including the dihydroxycompound (A) to react with the carbonic acid diester in the presence ofthe polymerization catalyst.

<Carbonic Acid Diester>

Examples of the carbonic acid diester to be used in the method ofproducing the polycarbonate resin include diphenyl carbonate,substituted diphenyl carbonates typified by ditolyl carbonate, dimethylcarbonate, diethyl carbonate, and di-t-butyl carbonate, particularlypreferably diphenyl carbonate and substituted diphenyl carbonates. Thosecarbonic acid diesters may be used alone or as a mixture thereof.

The carbonic acid diester is preferably used at a molar ratio of from0.90 to 1.10 with respect to all the dihydroxy compounds to be used inthe reaction, and is more preferably used at a molar ratio of from 0.96to 1.04. When the molar ratio becomes less than 0.90, the amount of aterminal OH group of the produced polycarbonate resin increases, andhence the thermal stability of the polymer deteriorates or a desiredpolymer is not obtained in some cases. In addition, when the molar ratiobecomes more than 1.10, under the same conditions, the rate of an esterexchange reaction reduces and hence it becomes difficult to produce apolycarbonate resin having a desired molecular weight. Moreover, theamount of the carbonic acid diester remaining in the producedpolycarbonate copolymer increases, and the remaining carbonic aciddiester may be responsible for an odor at the time of the molding of thecopolymer or in a molded article thus obtained.

In an embodiment in which the first retardation layer 20 and the secondretardation layer 60 to be described later are used in combination, theretardation layer 20 may be preferably formed of a cyclic olefin-basedresin. The cyclic olefin-based resin is a generic term for resins eachpolymerized by using a cyclic olefin as a polymerization unit, andexamples thereof include resins disclosed in JP 01-240517 A, JP 03-14882A, and JP 03-122137 A. Specific examples thereof include: a ring-opening(co)polymer of the cyclic olefin, an addition polymer of the cyclicolefin, a copolymer (typically a random copolymer) of the cyclic olefinand an α-olefin, such as ethylene or propylene, and graft-modifiedproducts obtained by modifying the polymers with unsaturated carboxylicacids or derivatives thereof; and hydrogenated products thereof.Specific examples of the cyclic olefin include norbornene-basedmonomers. Examples of the norbornene-based monomers include: norbornene,alkyl and/or alkylidene substituted products thereof, such asκ-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene,5-butyl-2-norbornene, and 5-ethylidene-2-norbornene, and polar group(e.g., halogen) substituted products thereof; dicyclopentadiene and2,3-dihydrodicyclopentadiene; dimethanooctahydronaphthalene, alkyland/or alkylidene substituted products thereof, and polar group (e.g.,halogen) substituted products thereof, such as6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene,6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, and6-methoxycarbonyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene;and trimers or tetramers of cyclopentadiene, such as4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene and4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene.

In the present invention, any other cycloolefin that may be subjected toring-opening polymerization may be used in combination with thecycloolefin to the extent that the object of the present invention isnot impaired. Specific examples of such cycloolefin include compoundseach having one reactive double bond, such as cyclopentene, cyclooctene,and 5,6-dihydrodicyclopentadiene.

The number-average molecular weight (Mn) of the cyclic olefin-basedresin measured by a gel permeation chromatograph (GPC) method based on atoluene solvent is preferably from 25,000 to 200,000, more preferablyfrom 30,000 to 100,000, most preferably from 40,000 to 80,000. When thenumber-average molecular weight falls within the range, a film that isexcellent in mechanical strength and has satisfactory solubility,satisfactory formability, and satisfactory casting operability can beobtained.

The retardation layer 20 is obtained by, for example, stretching a filmformed from the resin. Any appropriate molding processing method may beadopted as a method of forming a film from the resin. Specific examplesthereof include a compression molding method, a transfer molding method,an injection molding method, an extrusion molding method, a blow moldingmethod, a powder forming method, an FRP molding method, a cast coatingmethod (e.g., a casting method), a calender molding method, and ahot-press method. Of those, an extrusion molding method or a castcoating method is preferred. This is because the extrusion moldingmethod or the cast coating method can increase the smoothness of thefilm to be obtained and provide satisfactory optical uniformity. Formingconditions may be appropriately set depending on, for example, thecomposition and kind of the resin to be used and desired characteristicsof the retardation layer. Many film products are commercially availableas the resin, and hence any one of the commercial films may be subjectedas it is to stretching treatment.

The stretching ratio of the film may vary depending on, for example, adesired in-plane retardation value and a desired thickness of theretardation layer, the kind of the resin to be used, the thickness ofthe film to be used, and a stretching temperature. Specifically, thestretching ratio is preferably from 1.75 times to 3.00 times, morepreferably from 1.80 times to 2.80 times, most preferably from 1.85times to 2.60 times. When the film is stretched at such ratio, aretardation layer having an in-plane retardation with which the effectsof the present invention can be appropriately exhibited can be obtained.

The stretching temperature of the film may vary depending on, forexample, the desired in-plane retardation value and the desiredthickness of the retardation layer, the kind of the resin to be used,the thickness of the film to be used, and the stretching ratio.Specifically, the stretching temperature is preferably from 125° C. to150° C., more preferably from 130° C. to 140° C., most preferably from130° C. to 135° C. When the film is stretched at such temperature, aretardation layer having an in-plane retardation with which the effectsof the present invention can be appropriately exhibited can be obtained.

Any appropriate stretching method may be adopted as a method ofstretching the film. Specifically, one kind of various stretchingmethods, such as free-end stretching, fixed-end stretching, free-endshrinkage, and fixed-end shrinkage, may be employed alone, or two ormore kinds thereof may be employed simultaneously or sequentially. Withregard to the stretching direction, the stretching may be performed invarious directions or dimensions, such as a horizontal direction, avertical direction, a thickness direction, and a diagonal direction.

In one embodiment, the retardation layer is formed by subjecting theresin film to free-end uniaxial stretching or fixed-end uniaxialstretching. The free-end uniaxial stretching is specifically, forexample, a method involving stretching the resin film between rollshaving different peripheral speeds while running the film in itslengthwise direction. The fixed-end uniaxial stretching is specifically,for example, a method involving stretching the resin film in itswidthwise direction (lateral direction) while running the film in itslongitudinal direction.

In another embodiment, the retardation layer is produced by obliquelystretching the elongated resin film in a direction at a predeterminedangle relative to its longitudinal direction in a continuous manner.When the oblique stretching is adopted, an elongated stretched filmhaving a predetermined alignment angle relative to the longitudinaldirection of the film (i.e., having a slow axis in a direction at apredetermined angle) is obtained. As a result, for example, aroll-to-roll process can be performed at the time of its lamination withthe polarizer, and hence a production process can be simplified. Theterm “roll-to-roll process” refers to a system involving laminatingfilms with their longitudinal directions aligned with each other whileconveying the films with rolls.

As a stretching machine to be used for the oblique stretching, forexample, there is given a tenter stretching machine capable of applyingfeeding forces, or tensile forces or take-up forces, having differentspeeds on left and right sides in a lateral direction and/or alongitudinal direction. Examples of the tenter stretching machineinclude a lateral uniaxial stretching machine and a simultaneous biaxialstretching machine, and any appropriate stretching machine may be usedas long as the elongated resin film can be continuously subjected to theoblique stretching.

A-4. Another Retardation Layer

As described above, another retardation layer (second retardation layer)60 can function as a λ/2 plate. The in-plane retardation Re(550) of suchretardation layer is from 180 nm to 320 nm, more preferably from 200 nmto 290 nm, still more preferably from 230 nm to 280 nm. The anotherretardation layer 60 typically has a refractive index ellipsoid ofnx>ny=nz or nx>ny>nz. The Nz coefficient of the another retardationlayer is, for example, from 0.9 to 2, preferably from 1 to 1.5, morepreferably from 1 to 1.3.

The thickness of the another retardation layer may be set so that thelayer may most appropriately function as a λ/2 plate. In other words,the thickness may be set so that a desired in-plane retardation may beobtained. Specifically, the thickness is preferably from 10 μm to 60 μm,more preferably from 30 μm to 50 μm.

The another retardation layer contains a resin having an absolute valueof a photoelastic coefficient of preferably 2.0×10⁻¹¹ m²/N or less, morepreferably from 2.0×10⁻¹³ m²/N to 1.5×10⁻¹¹ m²/N, still more preferablyfrom 1.0×10⁻¹² m²/N to 1.2×10⁻¹¹ m²/N. When the photoelastic coefficientfalls within such range, in the case where a shrinkage stress at thetime of the heating of the layer occurs, a change in retardation hardlyoccurs. Therefore, the formation of the retardation layer through theuse of a resin having such photoelastic coefficient can satisfactorilyprevent the heat unevenness of an organic EL display apparatus to beobtained.

The another retardation layer may show a reverse wavelength dispersioncharacteristic, i.e., a retardation value increasing with an increase inwavelength of measurement light, may show a positive wavelengthdispersion characteristic, i.e., a retardation value decreasing with anincrease in wavelength of measurement light, or may show a flatwavelength dispersion characteristic, i.e., a retardation value hardlychanging even when the wavelength of measurement light changes. Thelayer preferably shows a flat wavelength dispersion characteristic. Theadoption of a λ/4 plate (retardation layer) having a flat wavelengthdispersion characteristic can achieve an excellent antireflectioncharacteristic and an excellent reflection hue in an oblique direction.The retardation layer preferably has a ratio Re(450)/Re(550) of from0.99 to 1.03, and preferably has a ratio Re(650)/Re(550) of from 0.98 to1.02. The another retardation layer (second retardation layer) may bepreferably formed of a cyclic olefin-based resin. The cyclicolefin-based resin and a method of forming the second retardation layerare as described in the section A-3 for the first retardation layer.

A-5. Barrier Layer

The barrier layer 30 has barrier properties against moisture and a gas(e.g., oxygen). The water vapor transmittance (moisture permeability) ofthe barrier layer under the conditions of 40° C. and 90% RH ispreferably 0.2 g/m²/24 hr or less, more preferably 0.1 g/m²/24 hr orless, still more preferably 0.05 g/m²/24 hr or less. Meanwhile, a lowerlimit for the moisture permeability is, for example, 0.001 g/m²/24 hr,preferably 0.005 g/m²/24 hr. The gas barrier property of the barrierlayer under the conditions of 60° C. and 90% RH is preferably from1.0×10⁻⁷ g/m²/24 hr to 0.5 g/m²/24 hr, more preferably from 1.0×10⁻⁷g/m²/24 hr to 0.1 g/m²/24 hr. When the moisture permeability and the gasbarrier property fall within such ranges, in the case where thecircularly polarizing plate is bonded to an organic EL panel, theorganic EL panel can be satisfactorily protected from moisture andoxygen in air. In addition, the total light transmittance of the gasbarrier layer is preferably 70% or more, more preferably 75% or more,still more preferably 80% or more in terms of optical characteristics.

Any appropriate construction may be adopted for the barrier layer 30 aslong as the construction has the desired characteristics. In oneembodiment, the barrier layer 30 includes a laminated structure of aninorganic thin film and an anchor coat layer. In this case, the barrierlayer 30 may be formed on the retardation layer so that the inorganicthin film may be positioned on an organic EL panel side (side distantfrom the polarizer). In another embodiment, the inorganic thin film maybe directly formed on the retardation layer.

The inorganic thin film is formed of any appropriate inorganic compound.The inorganic thin film preferably contains at least one kind ofinorganic compound selected from the group consisting of an oxide, anitride, a hydride, and a composite compound thereof. Specifically, theinorganic compound may be not only the oxide, the nitride, or thehydride alone but also a composite compound of the oxide, the nitride,and/or the hydride. When such compound is used, the thin film can bemore excellent in transparency. The inorganic compound forming theinorganic thin film may have any appropriate structure. Specifically,the compound may have a perfect crystal structure, or may have anamorphous structure.

Examples of constituent elements for the inorganic compound includecarbon (C), silicon (Si), aluminum (Al), magnesium (Mg), calcium (Ca),potassium (K), zinc (Zn), tin (Sn), nickel (Ni), sodium (Na), boron (B),titanium (Ti), lead (Pb), zirconium (Zr), yttrium (Y), hydrocarbons,oxides, carbides, and nitrides thereof, and mixtures thereof. Thoseelements may be used alone or in combination thereof. Of those, carbon,silicon, and aluminum are preferably used. Specific examples of theinorganic compound include diamond-like carbon (DLC), silicon nitride(SiN_(x)), silicon oxide (SiO_(y)), aluminum oxide (AlO_(z)), andaluminum nitride. A value for the x of the SiN_(x) is preferably from0.3 to 2. A value for the y of the SiO_(y) is preferably from 1.3 to2.5. A value for the z of the AlO_(z) is preferably from 0.7 to 2.3. Ofthose, the silicon oxide or the aluminum oxide is particularlypreferred. This is because a high gas barrier property can be stablymaintained.

Any appropriate construction may be adopted for the inorganic thin film.Specifically, the inorganic thin film may be formed of a single layer,or may be a laminate of a plurality of layers. When the inorganic thinfilm is the laminate, the laminate is specifically, for example, athree-layer construction formed of an inorganic oxide layer, aninorganic nitride layer, and an inorganic oxide layer (e.g., an SiO_(y)layer, an SiN_(x) layer, and an SiO_(y) layer).

Any appropriate method may be adopted as a method of forming theinorganic thin film. Specific examples thereof include a vapordeposition method and a coating method. Of those, a vapor depositionmethod is preferred because a uniform thin film having a high barrierproperty is obtained. The vapor deposition method includes: a physicalvapor deposition method (PVD), such as vacuum deposition, ion plating,or sputtering; and a chemical vapor deposition method (CVD).

The thickness of the inorganic thin film is preferably from 0.1 nm to5,000 nm, more preferably from 0.5 nm to 1,000 nm, still more preferablyfrom 10 nm to 1,000 nm, particularly preferably from 30 nm to 500 nm,especially preferably from 50 nm to 200 nm. When the thickness fallswithin such range, an inorganic thin film that has a sufficient barrierproperty, does not cause cracking or peeling, and is excellent intransparency can be obtained.

Any appropriate material may be adopted as a formation material for theanchor coat layer. Examples of the material include a resin, ahydrocarbon, a metal, a metal oxide, and a metal nitride.

The anchor coat layer is formed of, for example, a resin composition. Aresin to be used in the resin composition may be a solvent-based resinor may be an aqueous resin. In addition, the resin may be athermoplastic resin, may be a thermosetting resin, or may be aphotocurable resin. Specific examples of the resin include apolyester-based resin, a urethane-based resin, an acrylic resin, anitrocellulose-based resin, a silicon-based resin, an alcoholic hydroxygroup-containing resin (e.g., a vinyl alcohol-based resin and anethylene vinyl alcohol-based resin), a vinyl-based modified resin, anisocyanate group-containing resin, a carbodiimide-based resin, analkoxyl group-containing resin, an epoxy-based resin, an oxazolinegroup-containing resin, a modified styrene-based resin, a modifiedsilicon-based resin, and an alkyl titanate.

In one embodiment, the resin composition contains a thermosetting resinor a photocurable resin. The thermosetting resin is, for example, aresin that can be cured by the application of thermal energy, and canforma transparent and flat surface after the curing. Typical examplesthereof include polycarbonate, polymethyl methacrylate, polyacrylate, amethyl phthalate homopolymer or copolymer, polyethylene terephthalate,polystyrene, diethylene glycol bisallyl carbonate, anacrylonitrile/styrene copolymer, poly(-4-methylpentene-1), a phenolresin, an epoxy resin, a cyanate resin, a maleimide resin, and apolyimide resin, a product obtained by modifying any of theabove-mentioned compounds with polyvinyl butyral, anacrylonitrile-butadiene rubber, a polyfunctional acrylate compound, orthe like, and a thermosetting resin obtained by modifying any of theabove-mentioned compounds with a thermoplastic resin, such as across-linked polyethylene resin, a cross-linked polyethylene/epoxyresin, a cross-linked polyethylene/cyanate resin, a polyphenyleneether/epoxy resin, or a polyphenylene ether/cyanate resin. Those resinsmay be used alone or in combination thereof. Examples of thephotocurable resin include: a resin composition formed of an acrylatecompound having a radical reactive unsaturated bond; a resin compositionformed of an acrylate compound and a mercapto compound having a thiolgroup; and a resin composition obtained by dissolving an oligomer, suchas epoxy acrylate, urethane acrylate, polyester acrylate, or polyetheracrylate, in a polyfunctional acrylate monomer. Those resins may be usedalone or in combination thereof.

In another embodiment, the resin composition contains at least one kindof resin selected from the group consisting of a polyester-based resin,a urethane-based resin, an acrylic resin, an isocyanate group-containingresin, an oxazoline group-containing resin, a carbodiimide-based resin,an alcoholic hydroxy group-containing resin, and a copolymer of theresins from the viewpoint of a gas barrier property. Of those, apolyester-based resin is preferred.

The polyester-based resin may be obtained by causing a polyvalentcarboxylic acid component and a polyhydric alcohol component to reactwith each other. Examples of the polyvalent carboxylic acid componentinclude terephthalic acid, isophthalic acid, adipic acid, sebacic acid,azelaic acid, o-phthalic acid, diphenylcarboxylic acid, anddimethylphthalic acid, and examples of the polyhydric alcohol componentinclude ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,1,4-butanediol, diethylene glycol, neopentyl glycol, dipropylene glycol,1,6-hexanediol, and bisphenol A.

With regard to the molecular weight of the resin compositionconstituting the anchor coat layer, its number-average molecular weightis preferably from 3,000 to 30,000, more preferably from 4,000 to28,000, still more preferably from 5,000 to 25,000 from the viewpointsof a gas barrier property and adhesiveness.

A silane coupling agent is preferably added to the resin compositionforming the anchor coat layer from the viewpoint of an improvement inadhesiveness between layers. Examples of the silane coupling agentinclude: epoxy group-containing silane coupling agents, such asβ-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,γ-glycidoxypropylmethyldiethoxysilane, andγ-glycidoxypropyltrimethoxysilane; amino group-containing silanecoupling agents, such as γ-aminopropyltrimethoxysilane,N-β(aminoethyl)γ-aminopropylmethyldiethoxysilane,N-β(aminoethyl)γ-aminopropyltrimethoxysilane, andN-β(aminoethyl)γ-aminopropyltriethoxysilane; and mixtures thereof.Preferred examples of the silane coupling agent includeγ-glycidoxypropyltrimethoxysilane and γ-aminopropyltrimethoxysilane fromthe viewpoint of the adhesiveness between layers. Those silane couplingagents may be used alone or in combination thereof. The silane couplingagent is added at a ratio of preferably from 0.1 mass % to 80 mass %,more preferably from 1 mass % to 50 mass % with respect to the resincomposition forming the anchor coat layer from the viewpoint of theadhesiveness.

The resin composition forming the anchor coat layer preferably containsa curing agent, and polyisocyanate is preferably used as the curingagent. Specific examples thereof include: aliphatic polyisocyanates,such as hexamethylene diisocyanate and dicyclohexylmethane diisocyanate;and aromatic polyisocyanates, such as xylene diisocyanate,tolylenediisocyanate, diphenylmethane diisocyanate, polymethylenepolyphenylene diisocyanate, tolidine diisocyanate, and naphthalenediisocyanate. A difunctional or higher polyisocyanate is particularlypreferred from the viewpoint of an improvement in barrier property.

In the resin composition forming the anchor coat layer, any appropriateadditive may be blended as required. Examples of such additive include:polyhydric alcohols, such as glycerin, ethylene glycol, polyethyleneglycol, and polypropylene glycol; aqueous epoxy resins; lower alcohols,such as methanol, ethanol, n-propanol, and isopropanol; ethers, such asethylene glycol monomethyl ether, propylene glycol monomethyl ether,propylene glycol diethyl ether, diethylene glycol monoethyl ether, andpropylene glycol monoethyl ether; esters, such as propylene glycolmonoacetate and ethylene glycol monoacetate; antioxidants; weatheringstabilizers; UV absorbers; antistatic agents; pigments; dyes;antimicrobial agents; lubricants; inorganic fillers; antiblockingagents; adhesives; and plasticizers. In addition, any appropriate resinor additive may be added for the purposes of, for example, improving thefilm formability of the resin composition and preventing a pinhole.

Preferred examples of the metal forming the anchor coat layer includechromium, aluminum, silicon, nickel, titanium, tin, iron, molybdenum,and alloys of two or more kinds thereof from the viewpoints of thebarrier property and the adhesiveness. In addition, as the metal oxideor the metal nitride, oxides and nitrides of the above-mentioned metalsare preferred from the viewpoints of the barrier property and theadhesiveness. Of those, chromium, silicon oxide, aluminum oxide,titanium oxide, silicon nitride, aluminum nitride, titanium nitride arepreferred, and silicon oxide and silicon nitride are more preferred.

The hydrocarbon forming the anchor coat layer is, for example,diamond-like carbon.

The thickness of the anchor coat layer is preferably from 0.1 nm to5,000 nm, more preferably from 10 nm to 2,000 nm, still more preferablyfrom 100 nm to 1,000 nm, particularly preferably from 300 nm to 600 nm.

Any appropriate method may be adopted as a method of forming the anchorcoat layer. When the resin composition is used, examples of theformation method include coating and immersion. Specific examples of thecoating method include a reverse roll coater, a gravure coater, a rodcoater, an air doctor coater, a spray, and a brush. A uniform anchorcoat layer can be formed by subjecting, after the coating or theimmersion, a coated layer or a layer formed by the immersion to anyappropriate drying treatment to evaporate a solvent. Examples of thedrying treatment include: heat drying, such as hot-air drying or dryingwith a heated roll; and infrared drying. A heating temperature is, forexample, from about 80° C. to about 200° C. The formed anchor coat layermay be subjected to cross-linking treatment based on irradiation with anenergy ray in order that its water resistance and durability may beimproved.

When the metal, the metal oxide, or the metal nitride is used, examplesof the formation method include a vapor deposition method and a coatingmethod. Of those, a vapor deposition method is preferred because auniform thin film having high adhesiveness is obtained. Typical examplesof the vapor deposition method include: a physical vapor depositionmethod (PVD), such as vacuum deposition, ion plating, or sputtering; anda chemical vapor deposition method (CVD).

In order to improve the applicability and adhesive property of theanchor coat layer formation material to the surface on which the anchorcoat layer is formed (in the present invention, the surface of theretardation layer), the surface may be subjected to any appropriatesurface treatment (e.g., chemical treatment or discharge treatment)before the application. In addition, the anchor coat layer may besubjected to such surface treatment before the formation of the barrierlayer.

A protective layer may be formed on the surface side (inorganic thinfilm side or pressure-sensitive adhesive layer side) of the barrierlayer. The protective layer is typically formed of a resin. The resinforming the protective layer may be a solvent-based resin or may be anaqueous resin. Specific examples thereof include a polyester-basedresin, a urethane-based resin, an acrylic resin, a polyvinylalcohol-based resin, an ethylene-unsaturated carboxylic acid copolymer,an ethylene vinyl alcohol-based resin, a vinyl-modified resin, anitrocellulose-based resin, a silicon-based resin, an isocyanate-basedresin, an epoxy-based resin, an oxazoline group-containing resin, amodified styrene-based resin, a modified silicon-based resin, and analkyl titanate. Those resins may be used alone or in combinationthereof. Inorganic particles may be added to the protective layer forimproving its barrier property, abrasion resistance, and slidingproperty. Examples of the inorganic particles include a silica sol, analumina sol, a particulate inorganic filler, and a layered inorganicfiller. Those particles may be used alone or in combination thereof. Theinorganic particles may be added by mixing, or may be added bypolymerizing a monomer of the resin in the presence of the inorganicparticles.

The resin forming the protective layer is preferably an aqueous resin interms of an improvement in gas barrier property of the inorganic thinfilm, and is more preferably a vinyl alcohol resin or an ethylene vinylalcohol resin. A blend of polyvinyl alcohol and an ethylene-unsaturatedcarboxylic acid copolymer is also suitable.

A method of forming the protective layer is the same as the method offorming the anchor coat layer involving using the resin compositiondescribed above. The thickness of the protective layer is preferablyfrom 0.05 μm to 10 μm, more preferably from 0.1 μm to 3 μm.

The barrier layer 30 may be a single layer or may include a plurality oflayers. The term “one barrier layer” as used herein means that thenumber of constituent unit layers each formed of the anchor coat layerand the inorganic thin film, and as required, the protective layer isone. In the case where the barrier layer includes a plurality of layers,the number of the constituent unit layers is preferably from 1 to 10,more preferably from 1 to 5. In this case, the respective constituentunit layers may be identical to or different from each other.

A-6. Pressure-Sensitive Adhesive Layer

As described above, the pressure-sensitive adhesive layer 40 has thebarrier function. In the case where the barrier function is imparted tothe pressure-sensitive adhesive layer of the circularly polarizingplate, a circularly polarizing plate having an excellent organic ELpanel-protecting function can be obtained by a synergistic effect withthe barrier layer. Further, an organic EL display apparatus can beproduced with production efficiency more excellent than that in the casewhere the barrier layer is formed on an organic EL panel. Apressure-sensitive adhesive having the barrier function is, for example,a rubber-based pressure-sensitive adhesive composition using arubber-based polymer as a base polymer.

Examples of the rubber-based polymer include: a conjugated diene-basedpolymer obtained by polymerizing one kind of conjugated diene compound,a conjugated diene-based copolymer obtained by polymerizing two or morekinds of conjugated diene compounds, and a conjugated diene-basedcopolymer obtained by copolymerizing a conjugated diene compound and anaromatic vinyl compound; and hydrogenated products thereof.

The conjugated diene compound is not particularly limited as long as thecompound is a monomer having a polymerizable conjugated diene. Specificexamples of the conjugated diene compound include 1,3-butadiene,isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene,3-methyl-1,3-pentadiene, 1,3-heptadiene, and 1,3-hexadiene. Of those,1,3-butadiene and isoprene are preferred from the viewpoint of the easeof industrial availability. The conjugated diene compounds may be usedalone or in combination thereof.

The aromatic vinyl compound is not particularly limited as long as thecompound is a monomer having an aromatic vinyl structure copolymerizablewith the conjugated diene compound. Specific examples of the aromaticvinyl compound include styrene, p-methylstyrene, α-methylstyrene,vinylethylbenzene, vinylxylene, vinylnaphthalene, and diphenylethylene.Of those, styrene is preferred from the viewpoint of the ease ofindustrial availability. The aromatic vinyl compounds may be used aloneor in combination thereof.

The diene-based copolymers may be random copolymers or may be blockcopolymers. In addition, a diene-based copolymer may be obtained bycopolymerizing a compound except the conjugated diene compound and thearomatic vinyl compound.

The conjugated diene-based copolymer obtained by copolymerizing theconjugated diene compound and the aromatic vinyl compound preferably hasa molar ratio “conjugated diene compound/aromatic vinyl compound” of theconjugated diene compound to the aromatic vinyl compound of from 10/90to 90/10 (mol %).

Specific examples of such conjugated diene-based (co)polymer include abutadiene rubber (BR), an isoprene rubber (IR), a styrene-butadienecopolymer (SBR), a butadiene-isoprene-styrene random copolymer, anisoprene-styrene random copolymer, a styrene-isoprene block copolymer(SIS), a butadiene-styrene copolymer, a styrene-ethylene-butadiene blockcopolymer (SEBS), and an acrylonitrile-butadiene rubber (NBR). The (co)polymers may be used alone or in combination thereof. Of those, anisoprene-styrene copolymer is preferred. In addition, hydrogenatedproducts thereof may be suitably used.

As the rubber-based polymer except the conjugated diene-based(co)polymer, for example, isobutylene (IB), astyrene-isobutylene-styrene block copolymer (SIBS), or astyrene-ethylene propylene copolymer-styrene block copolymer may beused. The rubber-based polymers may be used alone or in combinationthereof.

The rubber-based polymer that may be used in the present inventioncontains the conjugated diene-based (co)polymer at preferably 50 wt % ormore, more preferably 70 wt % or more, still more preferably 80 wt % ormore, particularly preferably 90 wt % or more in the entirety of therubber-based polymer. An upper limit for the content of the conjugateddiene-based (co)polymer is not particularly limited, and the content maybe 100 wt % (i.e., the rubber-based polymer may be formed only of theconjugated diene-based (co)polymer).

As described above, the pressure-sensitive adhesive composition containsthe rubber-based polymer as the base polymer. The content of therubber-based polymer in the pressure-sensitive adhesive composition ispreferably 40 wt % or more, more preferably 50 wt % or more, still morepreferably 60 wt % or more. An upper limit for the content of therubber-based polymer is not particularly limited, and the content is,for example, 90 wt % or less.

The pressure-sensitive adhesive composition may further contain anyappropriate additive in addition to the rubber-based polymer. Specificexamples of the additive include cross-linking agents (e.g.,polyisocyanate, an epoxy compound, and an alkyl etherified melaminecompound), tackifiers (e.g., a rosin derivative resin, a polyterpeneresin, a petroleum resin, an oil-soluble phenol resin, and avinyltoluene resin), plasticizers, fillers (e.g., a layered silicate anda clay material), and age inhibitors. The kinds, combination, additionamounts, and the like of the additives to be added to thepressure-sensitive adhesive composition may be appropriately set inaccordance with purposes. The content (total amount) of the additives inthe pressure-sensitive adhesive composition is preferably 60 wt % orless, more preferably 50 wt % or less, still more preferably 40 wt % orless.

The thickness of the pressure-sensitive adhesive layer 40 is, forexample, from about 1 μm to about 300 μm, preferably from 1 μm to 200μm, more preferably from 2 μm to 100 μm, still more preferably from 25μm to 100 μm.

As described above, the pressure-sensitive adhesive layer 40 has abarrier property, and typically has barrier properties against moistureand a gas (e.g., oxygen). The water vapor transmittance (moisturepermeability) of the pressure-sensitive adhesive layer under theconditions of 40° C. and 90% RH when the thickness of the layer is 100μm is preferably 200 g/m²/24 hr or less, more preferably 150 g/m²/24 hror less, still more preferably 100 g/m²/24 hr or less, particularlypreferably 70 g/m²/24 hr or less. A lower limit for the moisturepermeability is, for example, g/m²/24 hr, preferably 15 g/m²/24 hr. Whenthe moisture permeability of the pressure-sensitive adhesive layer fallswithin such range, in the case where the circularly polarizing plate isbonded to an organic EL panel, the organic EL panel can besatisfactorily protected from moisture and oxygen in air by asynergistic effect with the barrier properties of the barrier layer.

A peeling film is preferably bonded to the surface of thepressure-sensitive adhesive layer until the layer is used.

A-7. Protective Film

The protective film 50 is formed of any appropriate film that may beused as a protective layer for the polarizer. Specific examples of amaterial serving as a main component of the film include transparentresins, for example, a cellulose-based resin, such as triacetylcellulose(TAC), a polyester-based resin, a polyvinyl alcohol-based resin, apolycarbonate-based resin, a polyamide-based resin, a polyimide-basedresin, a polyether sulfone-based resin, a polysulfone-based resin, apolystyrene-based resin, a polynorbornene-based resin, apolyolefin-based resin, a (meth)acrylic resin, and an acetate-basedresin. Another example thereof is a thermosetting resin or a UV-curableresin, such as a (meth)acrylic resin, a urethane-based resin, a(meth)acrylic urethane-based resin, an epoxy-based resin, or asilicone-based resin. Still another example thereof is a glassy polymer,such as a siloxane-based polymer. In addition, a polymer film disclosedin JP 2001-343529 A (WO 01/37007 A1) may also be used. As a material forthe film, for example, there may be used a resin composition containinga thermoplastic resin having a substituted or unsubstituted imide groupin a side chain and a thermoplastic resin having a substituted orunsubstituted phenyl group and a nitrile group in a side chain. Anexample thereof is a resin composition containing an alternate copolymerformed of isobutene and N-methylmaleimide and an acrylonitrile-styrenecopolymer. The polymer film may be, for example, a product obtained bysubjecting the resin composition to extrusion molding.

The glass transition temperature (Tg) of the (meth)acrylic resin ispreferably 115° C. or more, more preferably 120° C. or more, still morepreferably 125° C. or more, particularly preferably 130° C. or morebecause excellent durability can be obtained. An upper limit for the Tgof the (meth)acrylic resin is not particularly limited, but ispreferably 170° C. or less from the viewpoint of formability or thelike.

Any appropriate (meth)acrylic resin may be adopted as the (meth)acrylicresin as long as the effects of the present invention are not impaired.Examples of the (meth)acrylic resin include poly(meth)acrylates, such aspolymethyl methacrylate, a methyl methacrylate-(meth)acrylic acidcopolymer, a methyl methacrylate-(meth)acrylate copolymer, a methylmethacrylate-acrylate-(meth)acrylic acid copolymer, a methyl(meth)acrylate-styrene copolymer (e.g., an MS resin), and a polymerhaving an alicyclic hydrocarbon group (e.g., a methylmetharylate-cyclohexyl methacrylate copolymer or a methylmethacrylate-norbornyl (meth)acrylate copolymer). Preferred examplesthereof include poly(C₁₋₆alkyl (meth)acrylates), such as polymethyl(meth)acrylate. A more preferred example thereof is a methylmethacrylate-based resin containing methyl methacrylate as a maincomponent (from 50 wt % to 100 wt %, preferably from 70 wt % to 100 wt%).

Specific examples of the (meth)acrylic resin include ACRYPET VH andACRYPET VRL20A manufactured by Mitsubishi Rayon Co., Ltd., a(meth)acrylic resin having a ring structure in the molecule disclosed inJP 2004-70296 A, and a (meth)acrylic resin with a high Tg obtained byintramolecular cross-linking or an intramolecular cyclization reaction.

The (meth)acrylic resin is particularly preferably a (meth)acrylic resinhaving a lactone ring structure because of having high heat resistance,high transparency, and high mechanical strength.

Examples of the (meth)acrylic resin having a lactone ring structureinclude (meth)acrylic resins each having a lactone ring structuredisclosed in JP 2000-230016 A, JP 2001-151814 A, JP 2002-120326 A, JP2002-254544 A, and JP 2005-146084 A.

The mass-average molecular weight (sometimes referred to asweight-average molecular weight) of the (meth)acrylic resin having alactone ring structure is preferably from 1,000 to 2,000,000, morepreferably from 5,000 to 1,000,000, still more preferably from 10,000 to500,000, particularly preferably from 50,000 to 500,000.

The glass transition temperature (Tg) of the (meth)acrylic resin havinga lactone ring structure is preferably 115° C. or more, more preferably125° C. or more, still more preferably 130° C. or more, particularlypreferably 135° C. or more, most preferably 140° C. or more becauseexcellent durability can be obtained. An upper limit value for the Tg ofthe (meth)acrylic resin having a lactone ring structure is notparticularly limited, but is preferably 170° C. or less from theviewpoint of formability or the like.

The term“(meth)acrylic” as used herein refers to acrylic and/ormethacrylic.

The protective film 40 may be subjected to surface treatment, such ashard coat treatment, antireflection treatment, sticking preventiontreatment, or antiglare treatment, as required. The thickness of theprotective film is typically 5 mm or less, preferably 1 mm or less, morepreferably from 1 μm to 500 μm, still more preferably from 5 μm to 150μm.

When the inner protective film is adopted, it is preferred that theinner protective film be optically isotropic. The phrase “opticallyisotropic” as used herein means that the in-plane retardation Re(550) ofthe film is from 0 nm to 10 nm and the thickness direction retardationRth(550) thereof is from −10 nm to +10 nm. The Re(550) of the innerprotective film is preferably from 0 nm to 8 nm, more preferably from 0nm to 6 nm, still more preferably from 0 nm to 3 nm. The Rth(550) of theinner protective film is preferably from −8 nm to +8 nm, more preferablyfrom −6 nm to +6 nm, still more preferably from −3 nm to +3 nm. When theinner protective film is optically isotropic, the viewing angle of adisplay apparatus can be further enlarged and the color shift thereofcan be further reduced.

A-8. Method of Producing Circularly Polarizing Plate

A typical embodiment of a method of producing the circularly polarizingplate of the present invention is described below. This embodiment is asystem involving continuously laminating the polarizer and theretardation layer by the roll-to-roll process, and the circularlypolarizing plate can be produced by the system with extremely excellentproduction efficiency.

First, a retardation film constituting the retardation layer 20 isprepared. The retardation film is elongated and has a slow axis in adirection at a predetermined angle relative to its longitudinaldirection. The material, characteristics, production method, and thelike of such retardation film are as described in the section A-3.

Next, a reinforcing film is bonded to one surface of the retardationfilm through intermediation of a pressure-sensitive adhesive by theroll-to-roll process. Thus, a laminate of the retardation film and thereinforcing film is obtained. The reinforcing film having appliedthereto the pressure-sensitive adhesive and the retardation film aretypically bonded to each other by the roll-to-roll process.

Any appropriate material may be adopted as a material for thereinforcing film. Examples thereof include a plastic, paper, a metalfilm, and a nonwoven fabric. Of those, a plastic is preferred. Thereinforcing film may include one kind of material, or may include two ormore kinds of materials. For example, the film may include two or morekinds of plastics.

Examples of the plastic include a polyester-based resin, apolyamide-based resin, and a polyolefin-based resin. Examples of thepolyester-based resin include polyethylene terephthalate, polybutyleneterephthalate, and polyethylene naphthalate. Examples of thepolyolefin-based resin include a homopolymer of an olefin monomer and acopolymer of an olefin monomer. Specific examples of thepolyolefin-based resin include: homopolypropylenes; propylene-basedcopolymers, such as a block, random, or graft propylene-based copolymerhaving an ethylene component as a copolymerization component;Reactor-TPO; ethylene-based polymers of low density, high density,linear low density, or ultra low density; and ethylene-based copolymers,such as an ethylene-propylene copolymer, an ethylene-vinyl acetatecopolymer, an ethylene-methyl acrylate copolymer, an ethylene-ethylacrylate copolymer, an ethylene-butyl acrylate copolymer, anethylene-methacrylic acid copolymer, and an ethylene-methyl methacrylatecopolymer. Of those, a polyester-based resin is preferred andpolyethylene terephthalate is more preferred. Such resin has highdimensional stability, high stiffness, and high heat resistance, and hasan advantage in that the resin is excellent in general-purpose propertyfrom the viewpoint that the resin can be a subsidiary material.

The reinforcing film may contain any appropriate additive as required.Examples of the additive include an antioxidant, a UV absorber, alightstabilizer, an antistatic agent, a filler, and a pigment. The kinds,number, and amounts of the additives may be appropriately set inaccordance with purposes. In particular, when the material for thereinforcing film is the plastic, two or more kinds of the additives arepreferably incorporated for the purpose of, for example, preventing thedeterioration of the film.

Any appropriate antioxidant may be adopted as the antioxidant. Examplesof such antioxidant include a phenol-based antioxidant, aphosphorus-based processing heat stabilizer, a lactone-based processingheat stabilizer, a sulfur-based heat stabilizer, and aphenol-phosphorus-based antioxidant. The content of the antioxidant ispreferably 1 part by weight or less, more preferably 0.5 part by weightor less, still more preferably from 0.01 part by weight to 0.2 part byweight with respect to 100 parts by weight of the base resin of thereinforcing film (when the reinforcing film is a blend, the blend is thebase resin).

Any appropriate UV absorber may be adopted as the UV absorber. Examplesof such UV absorber include a benzotriazole-based UV absorber, atriazine-based UV absorber, and a benzophenone-based UV absorber. Thecontent of the UV absorber is preferably 2 parts by weight or less, morepreferably 1 part by weight or less, still more preferably from 0.01part by weight to 0.5 part by weight with respect to 100 parts by weightof the base resin of the reinforcing film.

Any appropriate light stabilizer may be adopted as the light stabilizer.Examples of such light stabilizer include a hindered amine-based lightstabilizer and a benzoate-based light stabilizer. The content of thelight stabilizer is preferably 2 parts by weight or less, morepreferably 1 part by weight or less, still more preferably from 0.01part by weight to 0.5 part by weight with respect to 100 parts by weightof the base resin of the reinforcing film.

Any appropriate filler may be adopted as the filler. Such filler is, forexample, an inorganic filler. Specific examples of the inorganic fillerinclude carbon black, titanium oxide, and zinc oxide. The content of thefiller is preferably 20 parts by weight or less, more preferably 10parts by weight or less, still more preferably from 0.01 part by weightto 10 parts by weight with respect to 100 parts by weight of the baseresin forming the reinforcing film (when the reinforcing film is ablend, the blend is the base resin).

Further, preferred examples of the additive include inorganic,low-molecular weight-type, and high-molecular weight-type antistaticagents intended to impart antistatic properties, such as a surfactant,an inorganic salt, a polyhydric alcohol, a metal compound, and carbon.Of those, a high-molecular weight-type antistatic agent or carbon isparticularly preferred from the viewpoints of the prevention of thecontamination of the film and the maintenance of the pressure-sensitiveadhesive property thereof.

Any appropriate thickness may be adopted as the thickness of thereinforcing film. The thickness of the reinforcing film is preferablyfrom 5 μm to 300 μm, more preferably from 10 μm to 250 μm, still morepreferably from 15 μm to 200 μm, particularly preferably from 20 μm to150 μm. Further, the total thickness of the reinforcing film and thepressure-sensitive adhesive to be described later is preferably from 1time to 4 times as large as the thickness of the retardation film.

The reinforcing film may be a single layer, or may be a laminate of twoor more layers.

The product (GPa·μm) of the tensile modulus of elasticity (GPa) at 23°C. and thickness (μm) of the reinforcing film is preferably from 20 to500, more preferably from 30 to 300. The value may be controlled byadjusting the kinds and amounts of the formation material and additiveof the reinforcing film, and when the reinforcing film is a laminate, aratio between the thicknesses of the respective layers. When the productis less than 20 (GPa·μm), the tensility of the reinforcing film isinsufficient and hence a wrinkle occurs at the time of its laminationwith the retardation film to impair the appearance of the circularlypolarizing plate in some cases. When the product is more than 500(GPa·μm), the tensility of the reinforcing film is so strong that ahandling property at the time of its peeling from the retardation filmbecomes insufficient in some cases.

The linear expansion coefficient of the reinforcing film is preferablyas small as possible. The linear expansion coefficient is preferablyfrom 5 ppm/° C. to 50 ppm/° C., more preferably from 10 ppm/° C. to 30ppm/° C. The ratio at which the dimensions of the reinforcing film arechanged by heating is also preferably as small as possible. For example,a dimensional change ratio after heating at 180° C. for 5 minutes ispreferably from 0.1% to 5.0%, more preferably from 0.5% to 3.0%. When areinforcing film having a small linear expansion coefficient and/or asmall dimensional change ratio by heating is used, even under ahigh-temperature environment in a barrier layer-forming process, thedimensional change of the retardation film can be suppressed and hence achange in orientation of a molecule in the film can be alleviated. As aresult, the optical characteristics (e.g., a slow axis direction and aretardation value) of the retardation film can be satisfactorilymaintained.

In one embodiment, the reinforcing film is stretched. Stretchingconditions may vary depending on purposes, a desired linear expansioncoefficient, and the like. A stretching ratio is preferably from 1.5times to 10 times, more preferably from 3.0 times to 5.0 times. Astretching temperature is preferably from the glass transitiontemperature (Tg) of the reinforcing film to a temperature higher thanthe Tg by 50° C. (Tg+50° C.). The stretching is preferably biaxialstretching. This is because the anisotropy of each of thermal propertiesand mechanical properties in the surface of the film can be alleviated.A method for the biaxial stretching may be any one of a tentersimultaneous biaxial stretching method, and a sequential biaxialstretching method based on a roll and a tenter. A tubular method mayalso be used.

When such retardation film as described in the section A-3 and suchreinforcing film as described above are used, in the case where thelaminate of the retardation film and the reinforcing film is subjectedto a vapor deposition method (e.g., sputtering) for the formation of thebarrier layer, the following advantage is obtained. That is, aretardation film obtained by oblique stretching originally tends to havea large variation in orientation (slow axis direction), and a problem inthat the variation in orientation (slow axis direction) becomes largerowing to a thermal stimulus and/or a mechanical stimulus may occur.Further, when the laminate is placed under a high-temperatureenvironment in the vapor deposition method, the films may break ordeform. When such retardation film and reinforcing film as describedabove are used in combination, even in the case where the laminate isplaced under such high-temperature environment as used in the vapordeposition method, the optical characteristics and mechanicalcharacteristics of the retardation film can be maintained withinallowable ranges. Therefore, the barrier layer can be formed on thesurface of the retardation film obtained by the oblique stretching whilethe characteristics of the film are maintained. As a result, theretardation film having formed thereon the barrier layer can besubjected to the roll-to-roll process.

Any appropriate pressure-sensitive adhesive may be used as thepressure-sensitive adhesive for the reinforcing film. Specific examplesof the base polymer of the pressure-sensitive adhesive include a(meth)acrylic polymer, a rubber-based polymer, a silicone-based polymer,a polyurethane-based polymer, and a polyester-based polymer. Thepressure-sensitive adhesive preferably contains a (meth)acrylic polymerhaving, as a main component (monomer unit), a (meth)acrylic acid alkylester having an alkyl group having 1 to 20 carbon atoms. The term “maincomponent” means a monomer having the highest constituent ratio out ofthe monomer units (components) constituting the (meth)acrylic polymer.Details about such pressure-sensitive adhesive are disclosed in, forexample, JP 2014-141649 A, and the corresponding disclosure isincorporated herein by reference.

Next, the barrier layer is formed on the surface of the retardation filmof the laminate of the retardation film and the reinforcing film. Inmore detail, the anchor coat layer is formed on the surface of theretardation film, and the inorganic thin film is formed on the surfaceof the anchor coat layer. The protective layer is formed on the surfaceof the inorganic thin film as required. The materials, formationmethods, and the like of the anchor coat layer, the inorganic thin film,and the protective layer are as described in the section A-5.

Heat treatment may be performed after the formation of the anchor coatlayer, after the formation of the inorganic thin film, and/or after theformation of the protective layer. When the heat treatment is performed,the barrier properties and film quality of the barrier layer to beobtained can be stabilized. In addition, air bubbles can be finelydispersed in the barrier layer to be obtained, and hence an adverseeffect caused by the air bubbles can be prevented. Any appropriatemethod may be adopted as a heating method in the heat treatment.Specific examples thereof include: a method involving storing theresultant laminate in an oven or a thermostatic chamber set to apredetermined temperature; a method involving blowing hot air againstthe laminate; a method involving heating the laminate with an infraredheater; a method involving irradiating the laminate with light throughthe use of a lamp; a method involving bringing the laminate into contactwith a heated roll or a hot plate to directly apply heat thereto; and amethod involving irradiating the laminate with a microwave. The heattreatment can be performed in a production process for the barrier layerby incorporating a heating apparatus into part of a film-producingapparatus, such as a coater or a slitter.

Any appropriate conditions may be adopted as conditions for the heattreatment in accordance with, for example, the structure, formationmaterial, and thickness of the barrier layer. A heat treatmenttemperature is typically a temperature equal to or less than the meltingpoint of the retardation film, and is preferably a temperature that doesnot adversely affect the optical characteristics and mechanicalcharacteristics of the retardation film. Specifically, the heattreatment temperature is preferably 60° C. or more, more preferably 70°C. or more because a treatment time necessary for the expression of theeffect of the heat treatment can be moderately set. Meanwhile, an upperlimit for the heat treatment temperature is, for example, 200° C.,preferably 160° C. from the viewpoint of the prevention of reductions inbarrier properties of the barrier layer. A heat treatment time maydepend on the heat treatment temperature. For example, when the heattreatment temperature is 150° C., the heat treatment time may be fromabout 3 minutes to about 60 minutes.

Thus, an optical laminate (intermediate for a circularly polarizingplate) having a construction “barrier layer/retardation film/reinforcingfilm” is produced. As is apparent from the foregoing description, theoptical laminate in this embodiment is elongated (roll shape in thedescribed example). As described above, when a specific retardation filmand a specific reinforcing film are used in combination, the barrierlayer can be formed on the surface of the retardation film obtained bythe oblique stretching while the optical characteristics and mechanicalcharacteristics of the film are maintained. Therefore, the retardationfilm having formed thereon the barrier layer can be subjected to theroll-to-roll process. That is, the optical laminate thus obtained is oneresult actually obtained in the present invention, and is one means forachieving the circularly polarizing plate of the present invention andan excellent effect thereof.

Next, the reinforcing film is peeled from the optical laminate, and thepolarizer is bonded to the peeled surface by the roll-to-roll process.In one embodiment, the laminate of the barrier layer and the retardationfilm obtained by peeling the reinforcing film, and a polarizing plate(laminate of the polarizer and the protective film) are bonded to eachother by the roll-to-roll process so that the polarizer may be adjacentto the retardation film. In another embodiment, the laminate of thebarrier layer and the retardation film, the polarizer, and theprotective film are collectively bonded to each other by theroll-to-roll process. In still another embodiment, the laminate of thebarrier layer and the retardation film, and the polarizer are bonded toeach other by the roll-to-roll process, and then the protective film isbonded to the resultant by the roll-to-roll process. The polarizingplate or the polarizer is elongated (roll shape in the describedexample), and has an absorption axis in its longitudinal direction. Inthe embodiment of the present invention, as described above, the barrierlayer can be formed on the retardation film having the slow axis in anoblique direction (direction at a predetermined angle relative to itslongitudinal direction), and hence lamination by the roll-to-rollprocess can be performed by using a polarizer obtained by typicallongitudinal uniaxial stretching.

Finally, the pressure-sensitive adhesive layer is formed on the surfaceof the barrier layer. The pressure-sensitive adhesive constituting thepressure-sensitive adhesive layer is as described in the section A-6.

Thus, the circularly polarizing plate of the present invention isobtained.

The case where the retardation layer 20 is used alone has been describedas a typical example of the method of producing the circularlypolarizing plate based on the roll-to-roll process. However, it isobvious to a person skilled in the art that the same procedure isapplicable to the case where the first retardation layer 20 and thesecond retardation layer 60 are used in combination. Specifically, alaminate of the retardation film constituting the first retardationlayer 20 and a retardation film constituting the second retardationlayer 60 only needs to be used instead of the retardation filmconstituting the retardation layer 20.

The circularly polarizing plate of the present invention may be producedby a so-called batch system. That is, the retardation film having formedthereon the barrier layer and the polarizing plate (laminate of thepolarizer and the protective film) may be bonded to each other afterhaving been cut into predetermined sizes. Alternatively, the retardationfilm having formed thereon the barrier layer, the polarizer, and theprotective film may be bonded to each other after having been cut intorespective predetermined sizes. The batch system eliminates the need forthe control of the angle between the absorption axis of the polarizerand the slow axis of the retardation film in a roll state, and hence aretardation film obtained by longitudinal stretching or lateralstretching can be used.

B. Organic EL Display Apparatus

An organic EL display apparatus of the present invention includes thecircularly polarizing plate described in the section A on its viewerside. The circularly polarizing plate is laminated so that thepressure-sensitive adhesive layer may be positioned on an organic ELpanel side (the polarizer may be positioned on the viewer side).

EXAMPLES

The present invention is specifically described below byway of Examples.However, the present invention is not limited by these Examples. Methodsof measuring the respective characteristics are as described below.

(1) Heat Resistance

Circularly polarizing plates obtained in Examples and ComparativeExamples were each cut into a size measuring 50 mm by 50 mm to be usedas a measurement sample. The measurement sample was bonded to a quartzglass, and the resultant was stored in an oven at 95° C. for 500 hours,followed by the measurement of a variation in hue value after thestorage with respect to its hue value before the storage. The hue valuewas measured with “DOT-3” manufactured by Murakami Color ResearchLaboratory Co., Ltd.

(2) Moisture Permeability

The circularly polarizing plates obtained in Examples and ComparativeExamples were each cut into a circular shape having a diameter of 10 cmto be used as a measurement sample. The moisture permeability of themeasurement sample was measured with “DELTAPERM” manufactured byTechnolox under the test conditions of 40° C. and 90% RH. The moisturepermeability of the circularly polarizing plate of Comparative Example 2was measured with “PERMTRAN” manufactured by MOCON, Inc. under the testconditions of 40° C. and 90% RH because the moisture permeabilityexceeded the measurement upper limit value of the former apparatus.

Example 1

A commercial polyvinyl alcohol (PVA) film (“VF-PS” manufactured byKuraray Co., Ltd.) was dyed in an aqueous solution containing iodine,and was then uniaxially stretched at about 6 times in an aqueoussolution containing boric acid between rolls having different speedratios to provide an elongated polarizer (thickness: 30 μm). A ratio K/Ibetween an iodine concentration (wt %) and a potassium concentration (wt%) in the polarizer was 0.402. A commercial TAC film (“TD80UL”manufactured by Fuji Photo Film Co., Ltd., thickness: 80 μm) was bondedas a protective film to one surface of the polarizer with a PVA-basedadhesive. Thus, a polarizing plate having a construction“polarizer/protective film” was obtained. The polarizing plate waspunched into a size measuring 20 cm long by 30 cm wide. At this time,the punching was performed so that the absorption axis of the polarizerserved as a longitudinal direction.

Meanwhile, a commercial elongated norbornene-based resin film (“ZEONOR”manufactured by Zeon Corporation, thickness: 50 μm) was stretched at1.52 times to provide a retardation film (thickness: 35 μm) having anRe(550) of 140 nm. A barrier layer (thickness: 150 nm) was formed on theretardation film. Thus, a laminate of the barrier layer and theretardation layer was obtained. An SiO_(x) film was formed as thebarrier layer by a sputtering method involving using an SiO target. Themoisture permeability of the barrier layer was 0.05 g/m²/24 hr.

The polarizing plate, and the laminate of the barrier layer and theretardation layer obtained in the foregoing were bonded to each otherthrough intermediation of an acrylic pressure-sensitive adhesive so thatthe polarizer and the retardation layer were adjacent to each other. Atthis time, the bonding was performed so that the slow axis of theretardation layer was positioned at 45° in a counterclockwise directionrelative to the absorption axis of the polarizer.

Finally, a pressure-sensitive adhesive layer (thickness: 50 μm) having abarrier function was formed on the surface of the barrier layer. Thus, acircularly polarizing plate having a construction “protectivefilm/polarizer/retardation layer (λ/4 plate)/barrierlayer/pressure-sensitive adhesive layer” was obtained. Apressure-sensitive adhesive produced as follows was used as apressure-sensitive adhesive constituting the pressure-sensitive adhesivelayer: 100 parts by weight of a styrene-ethylene-propylenecopolymer-styrene block copolymer (manufactured by Kuraray Co., Ltd.,trade name: “SEPTON 2063”, styrene content: 13 wt %) was compounded with10 parts by weight of polybutene (manufactured by JX Nippon Oil & EnergyCorporation, trade name: “NISSEKI POLYBUTENE HV-300”), 40 parts byweight of a terpene phenol tackifier (manufactured by Yasuhara ChemicalCo., Ltd., trade name: “YS POLYSTER TH130”), and an aromatic tackifier(manufactured by Eastman Chemical Company, trade name: “PICCOLASTICA5”). The moisture permeability of the pressure-sensitive adhesive layerwas 10 g/m²/24 hr (in terms of 50 μm). The resultant circularlypolarizing plate was subjected to the evaluations (1) and (2). Theresults are shown in Table 1.

Example 2

A commercial elongated norbornene-based resin film (“ZEONOR”manufactured by Zeon Corporation, thickness: 75 μm) was stretched at2.55 times to provide a retardation film (thickness: 45 μm) having anRe(550) of 270 nm. The retardation film (second retardation layer) andthe retardation film (first retardation layer) obtained in Example 1were laminated, and then a barrier layer was formed on the surface ofthe first retardation layer in the same manner as in Example 1. Thus, alaminate of the barrier layer, the first retardation layer, and thesecond retardation layer was obtained. A circularly polarizing platehaving a construction “protective film/polarizer/second retardationlayer (λ/2 plate)/first retardation layer (λ/4 plate)/barrierlayer/pressure-sensitive adhesive layer” was obtained in the same manneras in Example 1 except that the laminate was used. The resultantcircularly polarizing plate was subjected to the evaluations (1) and(2). The results are shown in Table 1.

Example 3

A circularly polarizing plate having a construction “protectivefilm/polarizer/second retardation layer (λ/2 plate)/first retardationlayer (λ/4 plate)/barrier layer/pressure-sensitive adhesive layer” wasobtained in the same manner as in Example 2 except that a polarizerhaving a ratio K/I of 0.210 was used. The resultant circularlypolarizing plate was subjected to the evaluations (1) and (2). Theresults are shown in Table 1.

Comparative Example 1

A circularly polarizing plate having a construction “protectivefilm/polarizer/second retardation layer (λ/2 plate)/first retardationlayer (λ/4 plate)/pressure-sensitive adhesive layer” was obtained in thesame manner as in Example 2 except that: the barrier layer was notformed; and a typical acrylic pressure-sensitive adhesive layer wasformed. The resultant circularly polarizing plate was subjected to theevaluations (1) and (2). The results are shown in Table 1.

Comparative Example 2

A circularly polarizing plate having a construction “protectivefilm/polarizer/second retardation layer (λ/2 plate)/first retardationlayer (λ/4 plate)/pressure-sensitive adhesive layer” was obtained in thesame manner as in Example 2 except that the barrier layer was notformed. The resultant circularly polarizing plate was subjected to theevaluations (1) and (2). The results are shown in Table 1.

TABLE 1 Heat resistance Moisture permeability (variation in a value)(g/m²/24 hr) Example 1 7 8.5 × 10⁻³ Example 2 7 8.0 × 10⁻³ Example 3 41.0 × 10⁻² Comparative Example 1 3 20 Comparative Example 2 3 15

As is apparent from Table 1, the circularly polarizing plates ofExamples of the present invention are each extremely excellent inbarrier property (moisture permeability). Further, as is apparent fromcomparison between Example 2 and Example 3, a polarizing platesatisfying an excellent moisture permeability and excellent heatresistance at the same time is obtained by improving the heat resistanceof a polarizer through the adjustment of a ratio K/I.

INDUSTRIAL APPLICABILITY

The circularly polarizing plate of the present invention is suitablyused in an organic EL display apparatus.

REFERENCE SIGNS LIST

-   -   10 polarizer    -   20 retardation layer    -   30 barrier layer    -   40 pressure-sensitive adhesive layer    -   50 protective film    -   60 another retardation layer    -   100 circularly polarizing plate    -   101 circularly polarizing plate

The invention claimed is:
 1. A circularly polarizing plate for anorganic EL display apparatus, comprising in this order: a polarizer; aretardation layer functioning as a λ/4 plate; another retardation layerfunctioning as a λ/2 plate between the polarizer and the retardationlayer, a barrier layer; and a pressure-sensitive adhesive layer having abarrier function, wherein an angle formed between an absorption axis ofthe polarizer and a slow axis of the retardation layer is from 65° to85°, and an angle formed between the absorption axis of the polarizerand a slow axis of the another retardation layer is from 10° to 20°, thepolarizer is elongated and has the absorption axis in a longitudinaldirection thereof; and the retardation layer and the another retardationlayer are elongated, and the retardation layer has the slow axis in adirection at from 65° to 85° relative to a longitudinal directionthereof, and the another retardation layer has the slow axis in adirection at from 10° to 20° relative to a longitudinal directionthereof.
 2. The circularly polarizing plate for an organic EL displayapparatus according to claim 1, further comprising a protective filmbetween the polarizer and the retardation layer.
 3. The circularlypolarizing plate for an organic EL display apparatus according to claim1, further comprising a protective film between the polarizer and theanother retardation layer.
 4. The circularly polarizing plate for anorganic EL display apparatus according to claim 1, further comprising aprotective film on a side of the polarizer opposite to the retardationlayer.
 5. The circularly polarizing plate for an organic EL displayapparatus according to claim 1, wherein: the polarizer is elongated andhas the absorption axis in a longitudinal direction thereof; and theretardation layer is elongated and has the slow axis in a direction atfrom 35° to 55° relative to a longitudinal direction thereof.
 6. Thecircularly polarizing plate for an organic EL display apparatusaccording to claim 1, wherein a ratio K/I of a potassium content (wt %)to an iodine content (wt %) in the polarizer is from 0.180 to 0.235. 7.An organic EL display apparatus, comprising the circularly polarizingplate for an organic EL display apparatus of claim 1.